Method of preparing n,nu&#39;-diphenyl-p-phenylenediamine



Patented Apr. 11, 1950 METHOD OF PREPARING N,N-DIPHEN,YL-p- PHENYLENEDIAMI-NE' Herbert G. Stone, Kingsport, Tenn, assignor to Eastman Kodak Company, Rochester, N. Y., a

corporation of New Jersey No Drawing. Application December 19, 1947', Serial No. 792,831

7 Claims.

This invention relates to N,N'-diphenyl pphenylenediamine, and more particularly to an improved method for producing this compound by reacting hydroquinone with aniline in the pres- 2 4% hours at a pressure of 125 pounds per square inch. In. the course of this time, 39 /2 cc. of water was removed from the reaction vessel azeotropically. The reaction mass was then cooled and ence of an alkyl phosphate catalyst; 5 transferred to a distillation flask. The aniline N,fN-dipheny1 p-phenylenediamine is customwasremoved by distillation at reduced pressure, arily prepared by the reaction of aniline with pand the residue was subjected to vacuum distillaaminophenol or with hydroquinone. When the tion. At 0.5 mm. pressure, 31.6 grams of material condensation withp-aminophenol is employed, a distilled below 220 C.; 196.5 grams distilled becatalyst such as anhydrous hydrogen chloride is tween 220-225 C. and consisted entirely of the required. When hydroquinone is the starting desired N,N'-diphen1y p-phenylenediamine. This material, catalysts such as phosphoric acid, anrepresents a yield of 75.6%, of theoretical. iline phosphate, or sodium. dihydrogen phosphate Example U have been heretofore employed.

These prior processes generally give yields, of The Preparatlon qescnbed 1n Example I was the desired product of-the order of 75 0% repeated, except that the triethyl phosphate was ever, these reactions have certain disadvantages replaced Wlthtrimethyl p p t In is se, in that they develop an appreciable amount of yleld of 732% was Obtainedtarry substancesasby-productsand there is con- Example In siderable corrosion of the metal equipment in which the reactions are conducted which can be Asman steel reafctor was charged w g 6-1 attributed to the catalysts used. In fact, someamhne to hydroqumone molecular rat) wlth 2 times the tar formed during the reaction adheres grams of tnethyl phosphate per of hydro to the walls of the reacting vessel, and is difficult qumone as Catalyst Thls was run 7% hours at to remove. 300 C. at a pressure of l 25 pounds per square It is, therefore, an object of this invention to p unread-fled amhne was removed and provide an improved process for condensing ondistllling the residue under vacuum at 0.5 mm. droquinohe with aniline through the use of a pressure a yield of 80.5% of the theoretical yield catalyst which has little or no corrosive action on 'dlphenyl p'phenylenedlamme was ordinary steel equipment and does not readily 3Q tamedpromote the formation of tar. It is a further 010- Example IV ject of this invention to provide a more active A small steel pressure reactor was charged with sgzg g gg the condensatlon of hydmqumone 110 grams of hydroquinone, 280 grams of aniline,

I have discovered that the trialkyl phosphates 14 g g i ghl p are very suitable for catalyzing the reaction bet 15 was 6 o mamtamed thls tween hydroquinone and aniline, and that they emperature for a pressure of 125 do not readily promote the formation of tars or pounqs per Square Inch Water produqed by the of other undesirable by products The trialkyl reactio was removed from the reaction vessel phosphates, as employed in accordance with my 40 azeotropically. The reaction mass was then invention can he prepared by any of the methods cooled and transferred to a dist11lat1on flask. The known to the art. Since these phosphates are aniline was removed by distillation at reduced organic in nature, the desirable improvements pressmjenand: the resldue was subllected to obtained in the reaction may be due in part to uum j f- At pressure 40 grams t fa t t they are more soluble in the reaction of material d1stilled below 220 C., 167 .2 grams dismixture than catalysts heretofore commonly Y tilled between 220-225" C. and consisted entirely p1yed of the N,N-drphenyl p-phenylenedia mine. This The present invention is further illustrated in represents Weld of 643% of theoretlca'lthe follo i examples; While trimethyl phosphate and triethyl phosphate are the preferred trialkyl phosphates to be Example I employed in accordance with my invention, other A small steel pressure reactor was charged with trialkyl P p s ca be employed such as tri- 110 grams of hydroquinone, 280 grams of aniline, n-propyl phosphate, triisopropyl phosphate, tri- 1.6 grams of triethyl phosphate. This was heated n-butyl phosphate, triisobutyl phosphate, tri 13-hto 300 C. and maintained at this temperature for butoxyethyl phosphate, dimethoxy n-butoxyethyl 3 phosphate, triethoxyethyl phosphate, and diethoxyethyl n-butoxyethyl phosphate.

As will be noted from the examples, only small amounts of the catalyst are required for the reaction to give good yields. Condensation temperatures may be between 300 and 350 C. and pressures from 125 to 150 pounds per square inch may be employed.

I claim:

1. In a method of preparing N,N'-diphenyl p-phenylene-diamine which comprises condensing hydroquinone with aniline under elevated temperatures and pressures, the improvement which comprises carrying out the reaction in the presence of an organic phosphate catalyst selected from the group consisting of the trialkyl phosphates in which each alkyl group contains from 1 to 4 carbon atoms, and trialkoxyethyl phosphates in which each alkoxy group contains from 1 to 4 carbon atoms, said catalyst being particularly advantageous in that it has substantially no corrosive action on reaction equipment and is productive of substantially no tarry byproducts.

2. In a method of preparing N,N'-diphenyl pphenylenediamine which comprises condensing hydroquinone with aniline under elevated temperatures and pressures, the improvement which comprises carrying out the reaction in the presence of a trialkyl phosphate catalyst in which each alkyl group is a primary alkyl group containing from 1 to 4 carbon atoms, said catalyst being particularly advantageous in that it has substantially no corrosive action on reaction equipment and is productive of substantially no tarry by-products.

3. In a method of preparing N,N-diphenyl pphenylenediamine which comprises condensing hydroquinone with aniline under elevated temperatures and pressures, the improvement which comprises carrying out the reaction in the presence of a trialkoxyethyl phosphate in which each I alkoxy group is a primary alkoxy group containing from 1 to 4 carbon atoms, said catalyst being particularly advantageous in that it has substantially no corrosive action on reaction equipment and is productive of substantially no tarry by-products.

4. In the method of claim 1, the step which consists in conducting the condensation under the preferred conditions of a pressure of approximately pounds per square inch and at a temperature of approximately 300 C.

5. In a method of preparing N,N-diphenyl pphenylenediamine which comprises condensing hydroquinone with aniline under elevated temperatures and pressures in 1-6 molar ratio, the improvement which comprises carrying out the condensation in the presence of trimethyl phosphate catalyst, said catalyst being particularly advantageous in that it has substantially no corrosive action on reaction equipment and is productive of substantially no tarry Icy-products.

6. In a method of preparing N,N-diphenyl pphenylenediamine which comprises condensing hydroquinone with aniline in 1-6 molar ratio, the improvement which comprises carrying out the condensation in the presence of triethyl phosphate catalyst, said catalyst being particularly advantageous in that it has substantially no corrosive action on reaction equipment and is productive of substantially no tarry by-products.

i. In a method of preparing N,N'-diphenyl pphenylenediamine which comprises condensing hydroquinone with aniline in 1-6 molar ratio, the improvement which comprises carrying out, the condensation in the presence of 2 grams of triethyl phosphate per mol. of hydroquinone at a temperature of approximately 300 C. and at a pressure of approximately 125' pounds per square inch, said catalyst being particularly advantageous in that it has substantially no corrosive action on reaction equipment and is productive of substantially no tarry Icy-products.

HERBERT G. STONE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,028,074 Lauter Jan. 14, 1936 2,133,825 Mouser Oct. 18, 1938 2,237,866 Guinot Apr. 8, 1941 2,238,320 Hardman Apr. 15, 1941 

1. IN A METHOD OF PREPARING N,N''-DIPHENYL P-PHENYLENE-DIAMINE WHICH COMPRISES CONDENSING HYDROQUINONE WITH ANILINE UNDER ELEVATED TEMPERATURES AND PRESSURES, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT THE REACTION IN THE PRESENCE OF AN ORGANIC PHOSPHATE CATALYST SELECTED FROM THE GROUP CONSISTING OF THE TRIALKYL PHOSPHATES IN WHICH EACH ALKYL GROUP CONTAINS FROM 1 TO 4 CARBON ATOMS, AND TRIALKOXYETHYL PHOSPHATES IN WHICH EACH ALKOXY GROUP CONTAINS FROM 1 TO 4 CARBON ATOMS, SAID CATALYST BEING PARTICULARLY ADVANTAGEOUS IN THAT IT HAS SUBSTANTIALLY NO CORROSIVE ACTION ON REACTION EQUIPMENT AND IS PRODUCTIVE OF SUBSTANTIALLY NO TARRY BYPRODUCTS. 